US5498762AExpiredUtility

Ferroelectric liquid crystal device

68
Assignee: CANON KKPriority: Aug 31, 1993Filed: May 17, 1995Granted: Mar 12, 1996
Est. expiryAug 31, 2013(expired)· nominal 20-yr term from priority
Inventors:Ken Eguchi
C09K 2323/02H01B 1/128G02F 1/141H01B 1/127G02F 1/133711C09K 19/0225
68
PatentIndex Score
24
Cited by
8
References
25
Claims

Abstract

A ferroelectric liquid crystal device is constituted by a pair of substrates each having thereon an electrode and an alignment film, and a ferroelectric liquid crystal disposed between the substrates. The alignment film on at least one substrate comprises laminated layers of at least two species of electroconductive polymers having mutually different optical band gaps Eqopt. The ferroelectric liquid crystal device can effectively remove undesirable reverse electric field effect even when a liquid crystal having a large spontaneous polarization is used, and exhibits little change in threshold characteristic with time.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
       1. A ferroelectric liquid crystal device, comprising: a pair of substrates each having thereon an electrode and an alignment film, and a ferroelectric liquid crystal disposed between the substrates; wherein the alignment film on at least one substrate comprises laminated layers of at least two species of electroconductive polymers having mutually different optical band gaps Eq opt . 
     
     
       2. A device according to claim 1, wherein a first layer of electroconductive polymer in the alignment film disposed in contact with the liquid crystal has an Eq opt  which is larger than that of a second layer of electroconductive polymer in the alignment film disposed below the first layer. 
     
     
       3. A device according to claim 1, wherein the electroconductive polymers are selected from the group consisting of polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof; polyarylenevinylene and derivatives thereof, polyisothianaphthene, poly(phenylene-2,5-diyl), poly(pyridine-2,5-diyl), poly(2,2'-bipyridine-5,5-diyl), and poly(pyridine-5,2-diyl-thiophene-2,5-diyl). 
     
     
       4. A device according to claim 3, wherein the derivatives of polypyrrole, polythiophene and polyaniline are respectively represented by the following recurring units respectively: ##STR5## wherein X denotes --COR and R denotes --C n  H 2n+1  (n=0-12). 
     
     
       5. A device according to claim 1, wherein the ferroelectric liquid crystal has a spontaneous polarization of at least 10 nC/cm 2 . 
     
     
       6. A device according to claim 1, wherein the ferroelectric liquid crystal sequentially assumes isotropic phase, cholesteric phase, smectic A phase and chiral smectic phase. 
     
     
       7. A device according to claim 6, wherein the ferroelectric liquid crystal has a helical pitch of at least 0.8 μm at a mid temperature in its cholesteric phase range. 
     
     
       8. A device according to claim 1, wherein the ferroelectric liquid crystal has no cholesteric phase on temperature decrease. 
     
     
       9. A device according to claim 1, wherein the ferroelectric liquid crystal has a helical pitch of at most 0.5 μm in its chiral smectic phase. 
     
     
       10. A device according to claim 1, wherein the ferroelectric liquid crystal has been subjected to an AC electric field application treatment. 
     
     
       11. A device according to claim 1, wherein at least one of the alignment films has been subjected to a uniaxial alignment treatment. 
     
     
       12. A device according to claim 11, wherein the uniaxial aligning treatment is rubbing. 
     
     
       13. A device according to claim 1, which is driven by a multiplexing drive scheme. 
     
     
       14. A liquid crystal device, comprising: a pair of substrates each having thereon an electrode and an alignment film, and a liquid crystal disposed between the substrates, said liquid crystal assuming chiral smectic phase and having a spontaneous polarization of at least 10 nC/cm 2 , wherein the alignment film on at least one substrate comprises laminated layers of at least two species of electroconductive polymers having mutually different optical band gaps Eq opt . 
     
     
       15. A device according to claim 14, wherein a first layer of electroconductive polymer in the alignment film disposed in contact with the liquid crystal has an Eq opt  which is larger than that of a second layer of electroconductive polymer in the alignment film disposed below the first layer. 
     
     
       16. A device according to claim 14, wherein the electroconductive polymers are selected from the group consisting of polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof; polyarylenevinylene and derivatives thereof, polyisothianaphthene, poly(phenylene-2,5-diyl), poly(pyridine-2,5-diyl), poly(2,2'-bipyridine-5,5-diyl), and poly(pyridine-5,2-diyl-thiophene-2,5-diyl). 
     
     
       17. A device according to claim 16, wherein the derivatives of polypyrrole, polythiophene and polyaniline are respectively represented by the following recurring units, respectively: ##STR6## wherein X denotes --COR and R denotes --C n  H 2n+1  (n=0-12). 
     
     
       18. A device according to claim 14, wherein the ferroelectric liquid crystal sequentially assumes isotropic phase, cholesteric phase, smectic A phase and chiral smectic phase. 
     
     
       19. A device according to claim 18, wherein the ferroelectric liquid crystal has a helical pitch of at least 0.8 μm at a mid temperature in its cholesteric phase range. 
     
     
       20. A device according to claim 14, wherein the ferroelectric liquid crystal has no cholesteric phase on temperature decrease. 
     
     
       21. A device according to claim 14, wherein the ferroelectric liquid crystal has a helical pitch of at most 0.5 μm in its chiral smectic phase. 
     
     
       22. A device according to claim 14, wherein the ferroelectric liquid crystal has been subjected to an AC electric field application treatment. 
     
     
       23. A device according to claim 14, wherein at least one of the alignment films has been subjected to a uniaxial alignment treatment. 
     
     
       24. A device according to claim 23, wherein the uniaxial aligning treatment is rubbing. 
     
     
       25. A device according to claim 14, which is driven by a multiplexing drive scheme.

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